Laravel queued mailable with pdf attachement

gistfile1.txt

<?php

namespace App\Mail;

use Illuminate\Bus\Queueable;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;
use Illuminate\Contracts\Queue\ShouldQueue;
/**
 * Usage:
 *  
 *   Mail::to('test@example.com')->send(new HasPdfAttachment($pdf));
 */
class HasPdfAttachment extends Mailable implements ShouldQueue
{
    use Queueable, SerializesModels;

    protected $pdf;

    public function __construct($pdf)
    {
        $this->pdf = base64_encode($pdf);
    }

    public function build()
    {
        return $this->view('emails.layout')
            ->attachData(base64_decode($this->pdf), 'document.pdf', [
                'mime' => 'application/pdf',
            ]);
    }
}